Saturated Water ```Name: Nick Status: educator Age: 30s Location: N/A Country: N/A Date: 2000 ``` Question: One liter of air containing 4% water vapor by volume(saturated), contains how much liquid water? Replies: You could calculate this from the ideal gas equation of state, pV = nRT, where ```p = atmospheric pressure, V = volume of the sample (= 1 L in this case), n = the number of moles of gas (unknown in this case), R = the "universal gas constant," 0.0820575 L atm / (K mol),and T = the temperature in K; room temperature is about 298 K. ``` Solving this equation for n tells you how many moles of gas are present. 4% of that is water. Knowing that water weighs 18 g/mole, you can then determine the weight of the water in the 1-L sample of air. How can this be empirically demonstrated? Two ways I can think of: 1. Put the sealed sample in a freezer, and weigh the frost that forms on the inside of the container. 2. Place a dessicant in the sealed sample container, and weigh the dessicant after it has absorbed all the water. I have been unable to find this concept discussed in any chemistry references looked up so far. Perhaps you could direct me to a source where this is talked about. Here's a really good intro: http://pasture.ecn.purdue.edu/~tao/homepage210/useful/vapor_pr/sld001.htm You might be able to get something out of these sites as well: http://atmos.nmsu.edu/education_and_outreach/encyclopedia/humidity.htm http://www.crh.noaa.gov/lmk/soo/docu/humidity.htm http://www.uswcl.ars.ag.gov/exper/relhumeq.htm http://www.chem.sunysb.edu/hanson-foc/lesson13.htm http://library.thinkquest.org/12596/dalton.html http://www.chem.ualberta.ca/~plambeck/che/p101/p01044.htm There are many more! Just search on "partial pressure." Richard E. Barrans Jr., Ph.D. Assistant Director PG Research Foundation, Darien, Illinois Click here to return to the Chemistry Archives

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